PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Donald J Pliner sport, vikram sole, sz 8.5-9Dansko Black Leather Mules Clog Shoes Sz 40 Flaws , Womens Flatform Buckle Wedge Holiday Festival Peep Toe Ankle Strap Sandal , BCBG Paris Lovelees Women's Gray Leather Slip On Round Toe Ballet Flats Size 9 B , Womens Bm Bernie Mev Crystal Black Wedges Womens Size 41 US 10.5-11 Sandals , NWT Joe's Jeans Women's Kitty VI Slip-On Ballet Flat Shoes MSRP $89.00ROCKET DOGS Womens MARABEL Black Thai Silk Ballet Flats Size US 8M , Crocs Womens Wrap ColorLite Perforated Loafer Shoe , KS35 Orionn Closed Toe Slip On Loafers, Pewter , Mephisto Mary Jane Brown Leather Mary Jane Wedge Slip On Womens US 10J Crew 7 M Brown Leather Clogs Mules Career Casual CUTE! ExcellentSperrry Top Sider Bahama 2 Eye Sequin Boat Shoe Women size 6.5 , Lnea big gommus Black Leather Women Shoes size 39.5 US made in Italy , LifeStride Women's Vanity Slip-On Loafer Black Size 7.0 VfKp , samples shoes BALLERINE ETNIES HYKU BLACK GOLD WOMENGORGEOUS! COUP D'ETAT MINT GREEN METALLIC GENUINE LEATHER LOAFERS SIZE 9M , LOLA ESPELETA Mocassins FIRST tout cuir bleu 41 NEUF BOITENew Vans Womens Olive Green Skater High Top Classic Canvas Shoes Sz US 8.5 , Minnetonka Men's Casey Slipper Chocolate Suede Size 8 , Men's New Totes Memory Foam Slip-On Slippers L 9.5-10.5- Choice Color , TALBOTS Loafers Pink/Beige Leather Bowler Walking Athletic Shoes Sz 6.5 , Adidas Duramo 5 TR Women's Size 7 Trail Running Shoes Pink - Nice - Fast Ship , Asics Gel Sonoma 2 Trail Running Womens 7.5 Shoes T684N((07A14 , Skechers Women Black White 8.5 M Shape-Ups 11809 Walking Toning Sneakers , **Skechers Relaxed Fit: Empire - Take Charge Sneakers - Women's Size 8 - White , NEW BALANCE WOMANS RUNNING SHOES SIZE 8.5 B WR530WSPWomen's MOHI... Shoes 089111 Grey 38 Reliable Quality Athletic Shoeswomen's shoes D.A.T.E. ( date ) 7 () sneakers black white leather BX72-38New Balance 847 V2? 7 AA New in Box12386 Black Pink BKPK Skechers Shoes Memory Women Sport Slip On Mesh Walk Bungee
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."